There are numerous applications of elastomeric endless power transmission belts throughout industry where the load to be driven, operating conditions, and other considerations dictate the use of a wide belt having a plurality of spaced ribs which engage associated pulley grooves. A typical wide belt with such ribs is shown in U.S. Pat. No. 2,802,511. However, it will be seen that in a belt of the type disclosed in the above-mentioned patent the load-carrying section and the tension section of such belt are each made as a single unit or uniform thickness structure at each point or location across the width of the entire belt whereby this type of belt has a substantial thickness which results in the belt being very stiff.
It has also been proposed to provide so-called banded belts to obtain required belt width but some of these belts tend to whip and vibrate when operated under high loads and such belts are also not very flexible.
Belt flexibility has been provided in some single element belts by forming teeth in the compression section of such belts; however, a single element toothed belt cannot drive comparatively high loads and is noisy when operated in associated sheaves.